1. Field of the Invention
This invention relates to a multichambered heat exchanger structure for a rotary kiln and, more particularly, to a rotary kiln for lime and cement processing which operates at high temperatures. Each of these rotary kilns is a long, slightly inclined cylinder with a charge of limestone or product-to-be-treated introduced at the higher end and heated air flowing countercurrent thereto introduced at the lower end. The structure, which has a refractory brick interior and a steel shell exterior, has the heat exchanger medial the ends thereof. The heat exchanger splits the flowing charge for improved surface contact into multiple flows. The kiln structure is sufficiently large that the steel shell deflects and the heat exchanger hereof is constructed to resist both the shell deflection and the kiln operating forces.
2. Information Disclosure Statement
Rotary kilns have a long and interesting technological history with, what is believed to be the earliest rotary kiln patented in England in 1885. This rotary kiln, called the Ransome kiln, was mounted at a slight angle and lined with fireclay brick. The kiln was charged at the higher end and fired at the lower end.
In the past, rotary kilns have been equipped with heat exchanger structures sometimes called trefoils manufactured by Harbison-Walker Refractories, Inc., now a division of Dresser Industries, Inc. and other refractory companies. As seen in the three Wicken et al. patents, infra, the trefoil structure shown have dam arrangements or interconnected trefoil lobes. In the Wicken et al. specifications, the refractory bricks are described as having, "conventional complementing tongues and grooves to afford some degree of mechanical interlock." This teaches away from the structure described hereinbelow.
Although some devices for adjusting refractory block positions with respect to the kiln interior wall, such as Antill '971, infra, are known, each is distinguishable from this disclosure.
In preparing for this application, the following U.S. patents became known to the inventor hereof:
______________________________________ ITEM NO. U.S. PAT. NO. INVENTOR ISSUE DATE ______________________________________ 1. 1,431,530 C. H. Leicester 10/10/22 2. 1,534,475 A. H. Willett et al 04/21/25 3. 1,741,680 G. W. Davey 12/31/29 4. 2,341,971 P. W. Antill 02/15/44 5. 3,030,091 O. M. Wicken et al 04/17/62 6. 3,036,822 N. E. Anderson 05/29/62 7. 3,169,016 O. M. Wicken et al 02/09/65 8. 3,175,815 O. M. Wicken et al 03/30/65 9. 3,221,614 J. Pertien 12/07/65 10. 3,346,248 J. R. Martinet et al 10/10/67 11. 3,362,698 J. J. Cerny et al 01/09/68 12. 3,834,108 H. T. Ludvigsen 09/10/74 13. 4,543,893 M. Kunnecke 10/01/85 14. 4,846,677 R. J. Crivelli 07/11/89 15. 4,960,058 W. R. Materna 10/02/90 16. 4,975,049 H. L. Roenigk et al 12/04/90 ______________________________________
These became known to the inventor by the review of Class 432, Subclasses 118 and 119; Class 110, Subclass 338; and, Class 52, Subclasses 604, 605, and 608.
U.S. Pat. No. 1,431,530 - C. H. Lucister - Issued Oct. 10, 1922
Discloses interlocking brick for constructing walls and furnaces having in one plane alternating keys and recesses that can be arranged in half brick staggered interlocking manner.
U.S. Pat. No. 1,534,475 - A. H. Willett et al. - Issued Apr. 21, 1925
Discloses fire brick for sectional fire arches on locomotives. The bricks have a tongue and groove arrangement interlocking with one another and permit a directed flow of gases which maintains the combustion in the furnace.
U.S. Pat. No. 1,741,680 - G. W. Davey - Issued Dec. 31, 1929
Discloses furnace wall construction from slidably interlockable components which provide air cooled chambers adjacent the outer wall to keep the wall at a temperature below softening point.
U.S. Pat. No. 2,341,971 - P. W. Antill - Issued Feb. 15, 1944
Discloses a furnace wall sectionally supported by hanger castings forming an air-cooled, tied wall. The wall accepts bats of insulating material between supporting refractory blocks.
U.S. Pat. No. 3,030,091 - O. M. Witken et al - Issued Apr. 17, 1962
Discloses a rotary kiln with a trefoil heat exchanger with each section having at the downstream end a dam to prevent sifting of the material when the section is uppermost.
U.S. Pat. No. 3,036,822 - N. E. Anderson - Issued May 29, 1962
Discloses a rotary kiln with a partitioned section dividing the stream into six equal streams. The partitions are mounted to yokes exterior to the kiln shell which compensate for kiln deformation.
U.S. Pat. No. 3,169,016 and U.S. Pat. No. 3,175,815 - O. M. Wicken et al - Issued Feb. 9, 1965 and Mar. 30, 1965, respectively.
Discloses rotary kilns with trefoil heat exchangers. The trefoil spokes are apertured allowing material to be dropped through into the countercurrent flowing gases of the adjacent chamber.
U.S. Pat. No. 3,221,614 - J. Pertien - Issued Dec. 7, 1965
Discloses a keyed road paving block preventing transverse and longitudinal movement in response to traffic.
U.S. Pat. No. 3,346,248 - J. R. Martinet et al - Issued Oct. 10, 1967
Discloses a wedge-shaped, refractory block structure for rotary kilns. The blocks have recesses and protuberances that interlock and expansion or spacer plates thereon, which structures tolerate temperatures to 1,000.degree. F. without decomposing.
U.S. Pat. No. 3,362,698 - J. J. Cerny et al - Issued Jan. 9, 1968
Discloses a refractory lining structure for a rotary kiln. Interlocking bricks interlock with each other and with brick holders mounted on the kiln shell. Insulation is inserted between the shell and the refractory bricks.
U.S. Pat. No. 3,834,108 - H. J. Ludvigsen - Issued Sep. 10, 1974
Discloses a building element for walls with one side providing a regular brick pattern and the other providing an interlocking arrangement.
U.S. Pat. No. 4,543,897 - M. Kunnecke - Issued Oct. 1, 1985
Discloses a lining brick for a rotary kiln with an air space for insulating the shell and for retaining heat in the kiln.
U.S. Pat. No. 4,846,677 - R. J. Crivelli - Issued Jul. 11, 1989
Discloses a trefoil heat exchanger for a rotary kiln with buttressed axial end portions of poured-in-place castable refractory to prevent downhill sliding of the trefoil construction.
U.S. Pat. No. 4,960,058 - W. R. Materna - Issued Oct. 2, 1990
Discloses a self-positioning refractory structure similar in interlocking relationship to Cerny et al. '698, supra. The structure has positioning filler and wedge refractories defining the annular space about the kiln.
U.S. Pat. No. 4,975,049 - Roenigk et l - Issued Dec. 4, 1990
Discloses refractory block for nose ring of a rotary kiln. Each block has lateral and rotational adjustments that are self-aligning.
None of the known patents address the technical problems of structuring trefoils to withstand both the compressive and torsional forces as is addressed hereby.